Finger operated pumps for dispensing small amounts of liquid from a container are well known. See, for example, U.S. Pat Nos. 3,001,524 and 3,452,905. Such pumps are relatively complex and do not dispense a predetermined amount of liquid because the amount of liquid dispensed upon each actuation of the pump depends on the way in which the pump is actuated, i.e., the speed and stroke of the actuator affect the quantity of the liquid dispensed.
Particularly where medicaments are to be dispensed, it would be desirable to provide a mechanism which dispenses a predetermined quantity of liquid every time the dispenser is actuated irrespective of the force applied to the actuator.